1、Designation: F 2502 05Standard Specification and Test Methods forBioabsorbable Plates and Screws for Internal FixationImplants1This standard is issued under the fixed designation F 2502; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification and test methods covers a mechanicalcharacterization reference for hydrolytically
3、degradable poly-mer resin (from this point on referenced as “bioabsorbable”)plates and screws for orthopedic internal fixation.1.2 This specification establishes common terminology todescribe the size and other physical characteristics of bioab-sorbable implants and performance definitions related t
4、o theperformance of bioabsorbable devices.1.3 This specification establishes standard test methods toconsistently measure performance-related mechanical charac-teristics of bioabsorbable devices when tested under definedconditions of pretreatment, temperature, humidity, and testingmachine speed.1.4
5、This specification may not be appropriate for all bioab-sorbable devices. The user is cautioned to consider the appro-priateness of the standard in view of the particular bioabsorb-able device and its potential application.1.5 This standard does not purport to address all of thesafety concerns, if a
6、ny, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 790 Test Methods for Flexural Properties of Unr
7、einforcedand Reinforced Plastics and Electrical Insulating MaterialsE4 Practices for Load Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 122 Practice for Calculating Sample Size to Estimate,With a Specified Tolerable Error, the Average for aCharacteristic
8、of a Lot or ProcessE 1823 Terminology Relating to Fatigue and Fracture Test-ingF116 Specification for Medical Screwdriver BitsF 382 Specification and Test Method for Metallic BonePlatesF 543 Specification and Test Methods for Metallic MedicalBone ScrewsF 565 Practice for Care and Handling of Orthopa
9、edic Im-plants and InstrumentsF 1635 Test Method for in vitro Degradation Testing ofHydrolytically Degradable Polymer Resins and FabricatedForms for Surgical ImplantsF 1839 Specification for Rigid Polyurethane Foam for Useas a Standard Material for Testing Orthopaedic Devicesand InstrumentsF 1925 Sp
10、ecification for Virgin Poly (L-Lactic Acid) Resinfor Surgical Implants2.2 ISO Standards:3ISO 13781 Poly (L-Lactide) Resins and Fabricated Formsfor Surgical ImplantsIn Vitro Degradation TestingISO 14630 Non-Active Surgical ImplantsGeneral Re-quirementsISO 15814 Copolymers and Blends Based onPolylacti
11、deIn Vitro Degradation Testing3. Terminology3.1 Definitions:3.1.1 Unless otherwise defined in this specification, theterminology related to mechanical testing that is used in thesetest methods will be in accordance with the definitions ofTerminologies E6and E 1823, and Specifications F 382 andF 543.
12、3.2 General Definitions:3.2.1 bioabsorbable devicea class of implants that aredesigned to deteriorate by means of biological resorption oncethey are implanted into the body.1This specification and test methods is under the jurisdiction of ASTMCommittee F04 on Medical and Surgical Materials and Devic
13、es and is the directresponsibility of Subcommittee F04.21 on Osteosynthesis.Current edition approved Oct. 1, 2005. Published October 2005.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
14、information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3
15、.2.2 biological resorptionprocess by which degradedbiomaterials (that is, products of degradation) are eliminated orincorporated, or both, by means of physiological metabolicroutes.3.2.3 deterioration (of a bioabsorbable device)the actionor process that results in a reduction of mass or mechanicalpe
16、rformance properties, or both.3.2.4 hydrolytically degradable polymer (HDP)any poly-meric material in which the primary mechanism of chemicaldegradation in the body is by hydrolysis (water reacting withthe polymer resulting in cleavage of the chain).3.3 Definitions for Apparatus:3.3.1 data acquisiti
17、on devicethe data recorder shall besuitable to continuously record torque versus angle of rotation,as well as linear displacement, calibrated in units of Newton-metres for torque and degrees for angle of rotation. The valueof torque shall have a resolution of 5 % of torsional yieldstrength. The angu
18、lar displacement scale shall have a minimumsensitivity so as to enable an accurate offset measurementcapability for a 2 angular displacement (see A1.5.3).3.3.2 pilot holes in test blockpilot holes shall be drilled inthe test block for insertion and removal of the test specimen.See Specification F 54
19、3, Annex 2.3.3.3 test blockthe test block shall be fabricated from auniform material that conforms to Specification F 1839. SeeSpecification F 543, Annex 2.3.3.4 testing fixturethe torsion testing apparatus that is tobe used for applying the required torque to the specimen shallbe calibrated for the
20、 range of torques and rotational displace-ments used in the determination. A suitable testing fixture forthe torsional yield strength-maximum torque-breaking angletest is illustrated in Fig. A1.1.3.3.5 test specimenthe test specimen shall be a com-pletely fabricated and finished bioabsorbable bone s
21、crew.3.3.6 torque transducera transducer to translate the ap-plied torque into an electrical signal amenable to continuousrecording, calibrated over the range of torques, both in theclockwise and counterclockwise rotation, to be encountered inthe test method, shall be provided.3.3.7 torsional displa
22、cement transducera transducer totranslate the angle of twist into an electrical signal amenable tocontinuous recording, calibrated over the range of angles to beencountered in the test and an accuracy of 61 % of reading,both in the clockwise and counterclockwise rotation, shall beused.3.4 Definition
23、s for Screw Testing:3.4.1 anchora bioabsorbable device or a component of abioabsorbable device that provides the attachment to the bone.3.4.2 bone anchora bioabsorbable device that provides ameans to attach soft tissue to bone with a suture.3.4.3 insertion depth (mm)the linear advancement of thebioa
24、bsorbable device into the test block measured relative to itsseated position at the test blocks surface prior to testing.3.5 Definitions for Plate Testing:3.5.1 bone platea device with two or more holes or slots,or both, and a cross section that consists of at least twodimensions (width and thicknes
25、s), which generally are not thesame in magnitude. The device is intended to provide align-ment and fixation of two or more bone sections, primarily byspanning the fracture or defect.3.5.2 bone plate length, L (mm)the linear dimension ofthe bone plate measured along the longitudinal axis as illus-tra
26、ted in Fig. A4.2.3.5.3 bone plate thickness, b (mm)the linear dimension ofthe bone plate measured parallel to the screw hole axis asshown in Fig. A4.2. For a bone plate with a crescent section,the thickness is measured at the thickest point along thesection.3.5.4 bone plate width, w (mm)the linear d
27、imension of thebone plate measured perpendicular to both the length andthickness axes as shown in Fig. A4.2.4. Significance and Use4.1 Biodegradable devices are expected by intention todeteriorate over time once they are implanted into the body.This makes the removal operation obsolete, which is adv
28、anta-geous especially for pediatrics.4.2 While the polymer degrades due to hydrolytic reactionwith the environment, the mechanical performance of thedevice also deteriorates. The key to developing effectivefracture fixation systems based on biodegradable devices is toprovide an adequate level of fix
29、ation strength for a time framethat exceeds that expected for fracture healing. Once thefracture is healed, the device can be completely resorbed by thebody.4.3 Generally, biodegradable devices will be tested withsimilar test methods that are used to evaluate conventionalmetallic devices. In additio
30、n, one has to take into considerationthe pre-test conditioning requirements, handling requirements,and time-dependent mechanical property evaluations for bio-degradable devices.5. Materials and Manufacture5.1 Bioabsorbable devices may be fabricated from one ofthe following materials:5.1.1 l-lactide,
31、 d-lactide, d,l-lactide, glycolide, or otherknown hydrolytically degradable polymer resins or copoly-mers. (See ISO 13781, ISO 15814, Test Method F 1635, andSpecification F 1925.)5.2 The manufacturer is responsible to ensure that materialsused to manufacture bioabsorbable implants are suitable forim
32、planting into the body. Methods to evaluate a materialssuitability are described in ISO 14630.FIG. 1 Screw ParametersF25020525.3 All bioabsorbable devices made of materials that havean ASTM committee F04 or D20 standard designation or anISO designation shall meet those requirements given in theASTM
33、standards.5.4 Soaking SolutionA phosphate buffered saline (PBS)solution shall be used. The pH of the solution shall bemaintained at 7.4 6 0.2 (see Test Method F 1635, SectionX1.3). The pH should be monitored frequently and, if need be,the solution should be changed periodically in order to main-tain
34、 the pH within the acceptable limits.5.4.1 Other physiologic solutions may be substituted pro-vided the solution is properly buffered. An anti-microbialadditive should be used to inhibit the growth of microorgan-isms in the solution during the test period. The investigatormust demonstrate that the c
35、hosen antimicrobial does not affectthe degradation rate (see X1.3).5.5 Sample ContainerA self enclosed container capableof holding the test sample and the solution (see X1.4). Multiplesamples may be stored in the same container provided thatsuitable sample separation is maintained to allow fluid acc
36、essto each sample surface and to preclude sample to samplecontact. Each container must be sealable against solution lossdue to evaporation.5.6 Constant Temperature Bath or OvenAn aqueous bathor heated air oven capable of maintaining the samples andcontainers at physiologic temperatures (37 6 2C) for
37、 thespecified testing periods.5.7 pH MeterA pH metering device sensitive in thephysiological range (pH 6 to pH 8) with a precision of 0.02 orbetter.5.8 BalanceAcalibrated weighing device capable of mea-suring the weight of a sample to a precision of 0.1 % of itsinitial weight.6. Conditioning6.1 Cond
38、itioningCondition the test specimens in a suit-able solution (for example, PBS solution) and temperature untilit is time to be tested. Remove from solution and wipe offexcess. The specimens must be tested within1hofrinsing (seeTest Method F 1635). In addition to conditioning the testspecimen in suit
39、able solutions, if the test specimen is intendedfor use in a loaded physiological condition, it may be importantto address the additional influence of conditioning static orfatigue loads, or both, on the deterioration of the test specimen.Conditioning loads should be chosen that are representative o
40、fanticipated physiological conditions.6.1.1 Test ConditionsConduct tests at 23 6 2C (73.4 63.6F) and 50 6 5 % relative humidity, unless otherwisespecified. (Remove from solution, wipe excess, and test within1 h of removal.)7. Care and Handling7.1 Bioabsorbable devices should be cared for and handled
41、in accordance with Practice F 565, as appropriate.8. Performance Requirements8.1 Factors considered being important, but for whichvalues and test methods have not been established, are shearstrength of the head of a screw, shear strength of the threadedregion of a screw, and enzymatically degradable
42、 polymerresins.9. Driving Instruments9.1 Specification F116provides related dimensional infor-mation for several types of medical screwdrivers.10. General Requirements and PerformanceConsiderations10.1 The following properties may be important whendetermining the suitability of a screw for a particu
43、lar applica-tion. However, the test methods referenced as follows may notbe appropriate for all types of implant applications. The user iscautioned to consider the appropriateness of the test methods inview of the devices being tested and their potential application.10.1.1 Offset Yield Strength is t
44、he stress at which thestress-strain curve departs from linearity by a specified percentof deformation (offset).10.1.2 Torsional Strength is an important parameter toprevent screw breakage during insertion. The torsional strengthshall be determined using the test methods described in AnnexA1.10.1.3 A
45、xial Pullout Strength is an important parameter ifthe screw is subjected to axial tensile forces, or if the screw isfixed into poor quality or osteoporotic bone. The pulloutstrength may be determined using the test methods described inAnnex A3.10.1.4 Insertion Torque is an important parameter to avo
46、idfailure of the screw during insertion and to ensure that thescrew may be easily inserted by the surgeon. The insertiontorque should be much less than the torsional yield strength ofthe screw as well as that of the appropriate screwdriver bit. Theinsertion torque may be determined using the test me
47、thodsdescribed in Annex A2.10.1.5 Geometric ConsiderationsBone plates that are in-tended to be used with bone screws shall have design features(screw holes or slots) that conform or appropriately fit thecorresponding bone screw.10.1.6 Bending PropertiesCritical characteristics of boneplates for orth
48、opedic applications since the bone plate providesthe primary means of stabilizing the bone fragments. Addition-ally, the bending stiffness of the bone plate may directly affectthe rate and ability of healing.10.1.6.1 The relevant bending properties (bending stiffness,bending structural stiffness, an
49、d bending strength) shall bedetermined using the standard test method of Annex A4.11. Keywords11.1 bend testing; bone plates; bone screw; dimensions;insertion; pullout; shear; torsionF2502053ANNEXES(Mandatory Information)A1. TEST METHOD FOR DETERMINING THE TORSIONAL PROPERTIES OF BIOABSORBABLE BONE SCREWSA1.1 ScopeA1.1.1 This test method describes methods for torsiontesting in order to determine intrinsic and structural propertiesof bioabsorbable bone screws. The test method measures thetorsional yield strength, maximum torque, and breaking angleof t
